Infections in the post-transplant period are a leading cause of morbidity and mortality among solid organ transplant recipients and hematopoietic stem cell transplant recipient. In the last 3 years we have been involved in a prospective 25 center surveillance network (TRANSNET), screening over 18,000 transplant recipients and identifying over 1,200 proven and probable cases of invasive fungal infection (IFI). This data has led to improved understanding of the disease burden in the U.S. and has highlighted some of the major differences among transplant groups. The group has had limited ability to perform case-control trials of Important risk factors. The CDC-sponsored initiative "Organ Transplant Infection Detection and Prevention Program" is a timely and necessary next step toward the assessment of risk factors associated with the Development of IFIs, and to initiate prospective surveillance for important non-fungal pathogens. We propose to achieve the following aims:1) to perform prospective surveillance among OTRs and HSCTRs for proven and probable IFIs at 3 US transplant centers (UAB, University of Michigan, and University of Pennsylvania), and to develop exportable surveillance methodology;2) to perform case-control studies among patients at high risk for invasive mould infections to identify significant nosocomial and outpatient risk factors and to establish recommendations for prevention;3) to develop methodologies for conducting prospective surveillance for selected non-fungal pathogens (i.e. West Nile virus, respiratory viruses, and selected multiresistant bacteria); and 4) to establish a bank for fungi and clinical specimens. The achievement of these goals will provide critically important insights into the key modifiable risk factors associated with the development of IFIs. Moreover, the establishment of standard surveillance methodology across multiple sites will significantly improve the quality and ease of data collection for important pathogens. Finally, the establishment of a bank will be invaluable in the development and validation of newer diagnostic assays.